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Flashcards · J247 · Topic 6

Global challenges flashcards

34 cards on Topic 6, subtopics B6.1 to B6.3. Pick a subtopic or study them all.

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B6.1 Monitoring and maintaining the environment

Distribution vs abundance, and which sampling method suits each
Distribution: where organisms are found; use a transect with quadrats at regular intervals across a gradient. Abundance: how many there are; use random quadrats to avoid bias.
Eight 0.25 m² quadrats on an 800 m² hillside hold 30 plants in total. Estimate the population.
Mean = 30 ÷ 8 = 3.75 per quadrat. Per m² = 3.75 ÷ 0.25 = 15. Estimate = 15 × 800 = 12 000.
Capture-recapture: 35 snails marked; later 30 caught, 7 marked. Estimate, and the assumptions
(35 × 30) ÷ 7 = 150 snails. Assumes marks stay and do no harm, marked animals mix evenly, and no significant births, deaths or migration.
Equipment for field sampling: quadrat, pooter, nets, key
Quadrat: counts plants or slow animals in a known area (or percentage cover). Pooter: collects small insects by suction. Sweep and pond nets. Key: identifies organisms from their features.
Ways humans reduce biodiversity
Land use (forest clearance, building, draining wetlands); monoculture; hunting and poaching; pollution such as acid rain and sewage.
Ways humans protect biodiversity
Protecting species: laws against hunting, captive breeding, reintroduction, seed banks. Protecting habitats: nature reserves, restoring hedgerows and ponds, controlling pollution.
How are lichens used as indicator species?
Crusty lichens tolerate more sulfur dioxide; bushy lichens need cleaner air. Mapping lichen types shows an air-quality gradient.
Ecotourism: benefits and a limit
Links conservation to income: pays for rangers and monitoring, gives local people jobs and a reason to protect habitats. Limit: too many visitors can disturb wildlife.
Challenges of maintaining biodiversity
International agreements are hard to reach and enforce; monitoring needs money and trained staff; local people may lose income from land, hunting or fishing; illegal activity is hard to detect in remote areas.
How does low dissolved oxygen, or sulfur dioxide, change the distribution of species?Higher
Low dissolved oxygen (made worse by warmer water): high-oxygen species such as mayfly nymphs decline; bloodworms can remain. Sulfur dioxide in air: sensitive lichens disappear.

B6.2 Feeding the human race

Food security, and five threats to it
People can reliably get enough safe, nutritious food. Threats: increasing population, changing diets, new pests and pathogens, environmental change, and the cost and sustainability of inputs.
Why does a shift to more meat and dairy threaten food security?
Energy is lost at each trophic level, so producing animal food needs more land per unit of energy than growing crops for people.
Why do plants need nitrate, phosphate and potassium?
Nitrate: amino acids and proteins. Phosphate: DNA, ATP and membranes. Potassium: enzymes and water balance.
Eutrophication in steps
Fertiliser washes into water → algal bloom → light blocked, submerged plants die → decomposers respire aerobically and use up oxygen → fish and other animals suffocate.
Pesticides: benefits, risks, and how resistance spreads
Less crop lost, so higher yields. Risks: harm to non-target species such as pollinators, build-up along food chains, cost. A few pests are resistant by chance; they survive and breed, so resistance spreads.
Hydroponics: advantages and disadvantages
Roots in an aerated solution of mineral ions. Advantages: exact control of ions and pH, no soil pests or weeds, water recycled, works on poor soil. Disadvantages: high set-up and energy costs, skilled management, disease spreads in shared solution.
Biological control: examples, advantages and disadvantages
Using a predator, parasite or pathogen of the pest, e.g. ladybirds against aphids. No residues, specific, resistance less likely; but slow, incomplete, and the introduced species may become a pest.
Selective breeding: benefits and costs
More food from the same land; uniform produce. Costs: less genetic variation, so a new disease can wipe out a crop or herd; inbreeding raises inherited disorders; slow, over many generations.
Genetic engineering
A process that modifies the genome of an organism to introduce desirable characteristics. Because the genome is changed, the change is inherited. Transgenic: carrying a gene from another species.
Genetic engineering of bacteria: the stepsHigher
Isolate the gene; cut it out with a restriction enzyme, leaving sticky ends; cut the plasmid with the same enzyme; join with ligase to make a recombinant plasmid; add to host bacteria; grow on antibiotic agar so only transformed bacteria grow.
What does the antibiotic resistance marker on a plasmid show?Higher
Only bacteria that took up the plasmid can grow on antibiotic agar. It shows plasmid uptake, not that the right gene is present.
Benefits and risks of GM crops
Benefits: higher yield, fewer insecticide sprays for toxin-making crops, added nutrients (beta-carotene rice), drought or salt tolerance. Risks: gene flow to wild relatives, pest resistance, harm to non-target organisms, unknown long-term effects, seed cost.

B6.3 Monitoring and maintaining health

Communicable vs non-communicable disease
Communicable: caused by a pathogen and passed between hosts (influenza, cholera, malaria, athlete's foot). Non-communicable: not passed on; caused by genes, diet, lifestyle, environment or ageing (cystic fibrosis, scurvy, most cancers, type 2 diabetes).
How influenza, cholera, malaria and athlete's foot spread
Influenza (virus): droplets in the air. Cholera (bacterium): contaminated water and food. Malaria (protist): mosquito vector. Athlete's foot (fungus): direct contact, damp shared floors.
Tobacco mosaic virus, barley powdery mildew and crown gall
TMV (virus): mosaic leaf patches, less photosynthesis; spread by contact. Powdery mildew (fungus): white powdery growth; wind-blown spores. Crown gall (bacterium): galls at the stem base; enters wounds from soil or water.
Physical and chemical defences of plants
Physical: the waxy, waterproof leaf cuticle and the tough cellulose cell wall. Chemical: antimicrobial substances (e.g. allicin in garlic) that kill or slow bacteria and fungi.
Detecting plant disease: field vs lab methodsHigher
Field: observing symptoms against identification guides; microscopy of spores. Lab: antigen detection with monoclonal antibodies; DNA testing (PCR) compared with positive and negative controls. Field is quick and cheap; lab tests confirm the pathogen.
Non-specific defences of the human body
Skin; clots and scabs; nose hairs and mucus; cilia sweep mucus up the airways; stomach acid kills swallowed pathogens; lysozyme in tears breaks down bacterial cell walls; phagocytes engulf and digest any pathogen.
Primary vs secondary immune response, and how a vaccine uses it
Primary (first exposure): slow, few matching lymphocytes, less antibody. Secondary: fast and much larger, because memory cells are already present. A vaccine gives safe antigens, so memory cells form without illness.
How are monoclonal antibodies made, and one use?Higher
Inject an antigen into a mouse; take B lymphocytes making the antibody and fuse them with tumour cells to make hybridomas; select, clone and grow them; purify the antibody. Use: pregnancy tests detect hCG in urine.
Stages in testing a new medicine
Preclinical (cells, computer models, animals): toxicity, effect, dose. Phase 1: few healthy volunteers, safety and dose. Phase 2: few patients, effectiveness. Phase 3: many patients, against a placebo or current treatment, often double-blind.
Treatments for cardiovascular disease, with one drawback each
Lifestyle change: slow. Statins (lower cholesterol): possible muscle pain. Stent (holds artery open): clots, re-narrowing. Bypass: major surgery. Heart transplant: few donors, rejection.
Benign vs malignant tumours
Cancer is uncontrolled cell growth and division after mutations. Benign: stays in one place, does not invade, not cancer. Malignant: invades nearby tissue and spreads in the blood to form secondary tumours.
Why are transplanted stem cells rejected, and how is rejection reduced?
Donor cells carry different antigens, which the recipient's lymphocytes attack. Reduce it by tissue matching, immunosuppressant drugs, using the patient's own stem cells, or therapeutic cloning.

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